Troubleshooting The GE Series 90-70 PLC System

Welcome to PDF Electric and Supply Company troubleshooting series: Troubleshooting the GE Series 90-70 PLC System.

PDF Supply has a large inventory of GE 90-70 parts, and we’ve created this article to assist users with troubleshooting techniques.

Step 1: Inspect Power Supply Status Begin by checking the LEDs on the front of the power supply and CPU. A green Power LED on the power supply indicates proper functionality.

Note: The Series 90-70 has 7 different power supply modules.

Step 2: Check Power Supply Fuse If the Power LED is off, inspect the fuse inside the power supply door. If the fuse is intact but the LED remains off, the power supply likely needs replacement.

Step 3: Inspect CPU Power-Up Status If the power supply is confirmed good, move to the CPU. A green "OK" LED indicates the CPU has passed its power-up test. If it is off, consider replacing the CPU and/or memory card.

Note: The Series 90-70 includes 21 CPU module options.

Step 4: Inspect CPU Run Status A green "RUN" LED confirms the CPU is executing program logic. If this LED is off, ensure the I/O Enable switch inside the CPU door is correctly positioned.

Step 5: Inspect "ENABLE" LED This LED should be green, indicating no internal faults and a properly positioned I/O Enable switch. If this LED is off, check the switch position and fault tables.

Step 6: Inspect "MEM PROTECT" LED This LED lights only when the key switch is in MEMORY PROTECT mode. It is present on newer CPU versions.

Step 7: Inspect Battery Status A dead battery can cause the CPU to enter STOP mode during power cycles. Replace the battery while the system is powered to avoid losing the program.

Tip: Use the dual-battery connector feature to ensure continuous power during change-out.

Step 8: CPU Out of "RUN" Mode A common failure is when the "RUN" LED is off due to an incident that puts the CPU in STOP mode. Connect a programming unit to the RS-485 Serial Port and navigate to the fault tables in your software.

Step 9: View Fault Tables Two primary fault tables exist: CPU and I/O. These logs provide time stamped data to help pinpoint issues, including rack and slot identifiers. Clear the faults after each correction to log any future issues cleanly.

Step 10: Additional Support Options If you're still experiencing problems, PDF Supply offers multiple solutions:

• Expert repairs

• Repair with exchange credit

• Remanufactured units with a 3-year warranty

• New components

Contact PLG Automation
Email: sales@plgautomation.com
Phone: 800-906-9271